If there's one thing that superhero movie fans know to expect by now, it's that any major hero-centric film will likely feature plenty of Easter eggs. These references range from the obvious (a cameo by Marvel icon Stan Lee) to the subtle (the "freaks dressed like clowns" line in Batman v. Superman that was definitely a nod to the Joker), and all of them speak to a greater cinematic universe. Regardless of whether a film features Marvel or DC characters, it's bound to have plenty of shout-outs to the bigger superhero picture, and the newest movie in the genre is no exception. The Marvel references and Easter eggs in X-Men: Apocalypse may not be as plentiful as those in other films, but the ones that do exist will make fans watch the movie with an eagle eye.

Unlike most of its fellow superhero movies, Apocalypse actually isn't filled to the brim with references to the greater comic world. Yet the Easter eggs that do appear in the movie are all pretty important, and fans aren't going to want to miss a single one. Here are the 18 biggest references in X-Men: Apocalypse — but beware, because of course, there are plenty of spoilers to follow.

1. A Stan Lee Cameo

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As usual, Marvel icon Lee makes a brief cameo, this time as a suburban man who, along with his wife, watches in fear and shock as nukes soar out of the ground into the sky.

2. And One From Lee's Wife

Unlike most Marvel movies, Lee's wife, Joan, also makes a cameo, appearing alongside her husband as one half of the couple.

3. The Dark Phoenix Line

Relatively early on in Apocalypse, Jean Grey, after having a vision of the end of the earth, tells Professor X that she feels a "dark power" inside her that's growing larger — a nod to Dark Phoenix, the villainous character she becomes later in life.

4. Essex Corp

The post-credits scene ends on a shot of Essex Corp, the company run by Mister Sinister, a notorious Marvel villain. Perhaps he'll play a big role in the next Wolverine movie?

8. Caliban

9. Storm's Hair

After encountering Apocalypse, Storm changes her hair into a mohawk, which is the look her character rocks in the comics.

10. Blob

Towards the beginning of the movie, viewers watch a mutant fighting match between Angel — who becomes a central character — and Blob, who has no actual importance in the movie, but provides a fun cameo for X-Men fans nonetheless.

11. Major Stryker

The famous super villain makes a brief appearance in Apocalypse, and looks as sinister as ever.

12. Nina

It's hinted that Nina, Magneto's young daughter, has mutant abilities herself, as she seems to be able to control the actions of birds — until she's tragically killed by police.